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Purity Monitors - Guide

Normal Data Taking

The purity monitors operate autonomously and do not need any attention from the shifter other than monitoring data via the slow controls or the logbook. The shifter does not need to worry about turning them on or off. The purity monitor expert will take care of all of this.

What to watch for

There are only a few things a shifter ought to concern themselves with. The first is age of data. The second is the Q_A/Q_C value over an 8 hour period. Q_A is the charge arriving at the anode. Q_C is the charged that left the photocathode.

Age of Data

Currently, the slow controls sends a MAJOR alarm if the age of the purity monitor data is over 5 hours. If this MAJOR alarm appears, email the purity monitor expert. It's likely that the DAQ program has crashed and needs to be restarted. Don't be afraid, call me.

Declining Purity

As mentioned in the Overview for the purity monitor, the long monitor is the one to pay attention to. Plots from the purity monitor analysis appear automatically every 8 hours in the logbook. An example post can be found here. The most important plot to pay attention to is the Q_A/Q_C plot. In the plot, the measured values of Q_A and Q_C are plotted as a fucntion of time. On the plot are lines corresponding to values of Q_A/Q_C that correspond to lifetimes of 3 ms and 6 ms. If the values of Q_A/Q_C go below 3 ms, email the purity monitor expert.

An example of the Q_A/Q_C plot appears below: